Plating metals



S TATES WILLIAM J. WILDER, OF ST. LOUIS, MISSOURI.

PLATING METALS.

SPECIFICATION forming part of Letters Patent No. 604,201, dated May 17, 1898.

Application filed October 2 8, 18 9 7.

To all whom, it may concern; 7

Be it known that 1, WILLIAM J. WILDER, a citizen of the United States, residing in the city of St. Louis, in the State of Missouri, have invented certain new and useful Improvements in Plated Metals and in Processes of Producing the Same, of which the following is a specification.

As is well known, galvanized sheet iron and steel, though of great value and used in immense quantities in the industrial arts, have several serious defects. Among these are the unevenness of the coating, its brittleness, the weakness of its attachment to its base, its liability to be detached by-the rustling of the base beneath it, its tendency to crack and flake off when a sheet is bent at a sharp angle or doubled back, its liability to be detached from its base and destroyed by expansion and contraction, and its inability to resist the corrosive action of sulfur and gases usually present as impurities in the air of large cities.

The chief objects of my invention are, first, to provide an article of plated metal which, while possessing the virtues of galvanized iron and steel, will be free from their defects and at the same time cheap enough to enable it to compete with and displace them for all purposes for which they have heretofore been used, and, second, to provide a process for producing the desired product.

In manufacturing my improved plated metal I preferably proceed in the manner hereinafter described.

For the coating I prepare or have prepared an alloy whose preferred composition is substantially as follows: eighty-four per cent. by weight, of zinc fourteen per cent. by weight, of tin; 1.5 per cent, by weight, of lead, and .5 per cent, by weight, of aluminium.

The specified proportions, though considered the best, are not essential; nor is it essential to use all of the metals mentioned.

The proportion of tin may be reduced as low as six per cent, or, on the other hand, increased to ninety per cent. of the whole, and what is subtracted from or added to the weight of the tin used may be added to or subtracted from the weight of the zinc, so as to have the joint weight of the zinc and tin about the same as in the formula. Where, however,

' the proportion of tinused is reduced, the heat used in preparing the alloy and in applying it to metal coated therewith has to be increased, and where the proportion of tin used is as low as six per cent. the heat which has to be used is so great as to endanger the zinc contained in the alloy, as well as the pot in which it is melted, and, moreover, the results are not so good, even where the other metals are not injured, as they are where the pre ferred proportion of tin is used. The objection to increasing the proportion of tin used is that it involves an increase in the cost of the finished sheets without materially improving their coating.

Lead is not an essential element of the alloy.

It is used in order to give it great fluidity when melted and so as to enable it to flow more freely and smoothly over the surface of a sheet being coated than the alloy does where lead is omitted, and its value is rather in the process of coating than in the coating when formed. Where less than one and ahalf per cent. of lead is used, the fluidity of the mixture is correspondingly diminished; but even where none at all is used good results may still be secured by using more care and skill than would otherwise be called for. The proportion of lead used may be increased to 2.5 per cent. without materially affecting the value of the alloy; but if substantially more than that is used the surplus does not combine with the other metals used, but sinks to the bottom of the melting-pot. In doing this it carries other metal with it and causes an undesirable waste.

Where the proportion of lead in the alloy is increased, the weight of either the zinc or tin, or both, may be decreased by subtracting from one or both enough metal to compensate for the lead added.

amount is mixed with the other metals the surplus aluminium will not combine with them, but will rise to the surface of the mixture and should be skimmed off. The more perfectly combined the elements of the alloy are the better it will answer as a coating.

In making the alloy the metals should preferably be melted together in the usual way and kept in the molten state and stirred occasionally until they are perfectly combined. This generally occupies from thirty-six to forty-eight hours, and I prefer to keep the elements of the alloy in the melted state and stir them occasionally for the latter period.

In practice I have prepared the alloy in the pot used in coating the sheets and have used the alloy as formed without allowing it to cool; but, as will be evident, the alloy may be either used as soon as made or allowed to harden and afterward remelted. Where, however, the alloy is allowed to cool slowly, the constituent metals tend to separate and, when melted, have to be reunited, which 00 cupies some hours. In making the alloy the heat used should be sufficient to melt all the metals which enter into it and not high enough to destroy or materially injure either of them.

The alloy when made may be used while in a molten state as a bath for coating iron and steel,- just as melted zinc is commonly used in making what is commonly termed gal vanized iron or steel, and the coating may be applied by dipping the sheets or articles to be coated into the molten bath and then withdrawing them or by passing them through the bath, according to either of the methods used by galvanizers. I prefer to keep the bath at a temperature between 600 and 900 Fahrenheit. The necessary heat depends largely upon the amount of tin used. WVhere as little as six per cent. of tin is used, I prefer 900; but where the preferred proportion of tin is used (fourteen per cent.) I prefer to keep the bath between 600 and 700 Fahrenheit. I seldom use less than seven per cent. of tin, and when I use that proportion I obtain good results by keeping the bath at a temperature between 700 and 800 Fahrenheit. I generally use the higher heat. All that is essential, however, is to keep the alloy fully melted on the one hand and on the other to avoid increasing the temperature of the bath high enough to injure either of the constituent metals.

The alloy above described may be applied as a coating to either iron or steel; but in the manufacture of plated sheets I prefer to use sheet-steel as a base. v

Before introducing the sheets or other articles into the bath they should be thoroughly cleansed, preferably in a suitable pickle, after the manner usual in galvanizing. If the sheets or other articles have any acid adhering to them when withdrawn from the pickle, it should preferably be thoroughly removed therefrom before they are coated. The sheets or other articles when coated should preferably be perfectly free from either rust or acid. After cleansing the sheets or other articles they should have a suitable flux applied to their surfaces. Any of the fluxes used by tin-platers will answer. It may be applied in the manner in which fluxes are usually applied in making galvanized iron and steel or in any other manner known in the art of plating sheet iron and steel.

After receiving a suitable flux the sheets or other articles to be coated may be introduced into the bath of molten alloy and withdrawn therefrom according to any of the methods now in use in plating with zinc or in any other suitable manner. Where either iron or .steel is treated in this way, the heat of the bath appears to alloy that portion of the coating next the base with the metal of the base, though at its own surface the coating appears to be composed solely of the alloy used as a bath. The union between them is perfect and cannot be affected either by expansion and contraction or bending the finished article.

The coating is as flexible as the coated base and so tough and tenacious that sheet steel or iron can be worked up into articles of manufacture as well after coating as before, in which it differs radically from galvanized iron and steel. As is well known, most articles of galvanized iron or steel are coated with zinc after they are made.

My improved coating is far superior to zinc in texture and appearance. The texture of the coating in its preferred form is fine, smooth, and homogeneous, and in appearance it resembles aluminium. In its power of resisting corrosive agents my plated metal is far superior to either galvanized iron or steel, and I judge from exhaustive tests that it is more desirable than tin-plate and superior to it for many purposes. It may be heated redhot without injury to the coating, and is superior to either galvanized iron or steel for making household utensils. For roofing and all other architectural sheet-metal work my sheets are superior to any other plated sheet metal with which I am acquainted.

I do not wish to be confined, when my claims are construed, to an alloy containing lead except where it is specified, or to one in which the metals entering into it are combined in the preferred proportions hereinbefore specified, and where I specify zinc, tin, and aluminium as contained in the coating I do not wish to be understood as excluding all other metals. Lead, for instance, may either be combined with the zinc, tin, and aluminium or entirely omitted, as has been hereinbefore explained.

I claim 1. As a new manufacture iron or steel having a coating of a flexible tenacious alloy, containing aluminium, tin and zinc.

2. As a new manufacture iron or steel having a coating of an alloy containing alu- IIO minium, lead, tin and zinc, substantially as described.

3. The process of preparing the herein-described new manufacture consisting in preparing a molten bath of an alloy containing aluminium, tin and zinc; cleansing iron or steel and applying a suitable flux and after applying the flux introducing the iron or steel into, and withdrawing it from, the bath, sub- I0 stantially as described.

4. The process of preparing the herein-de- 

